CN113846342A

CN113846342A - Inorganic-organic core-shell framework loaded low-dose noble metal palladium material, preparation thereof and application thereof in electrocatalytic dechlorination and hydrogenation reaction

Info

Publication number: CN113846342A
Application number: CN202111191179.XA
Authority: CN
Inventors: 赵浙菲; 俞丽; 郑华均
Original assignee: Zhejiang University of Technology ZJUT
Current assignee: Zhejiang University of Technology ZJUT
Priority date: 2021-10-13
Filing date: 2021-10-13
Publication date: 2021-12-28
Anticipated expiration: 2041-10-13
Also published as: CN113846342B

Abstract

The invention discloses an inorganic-organic core-shell framework loaded low-dose noble metal palladium material, and a preparation method and application thereof in electrocatalytic dechlorination and hydrogenation reactions; the method utilizes the in-situ self-polymerization of dopamine to polymerize dopamine on TiO with an array structure vertically grown on the surface of FTO₂TiO is wrapped by polydopamine around the one-dimensional nano-rod₂Inorganic-organic of nanorodsA core-shell structure; uniformly dispersing and loading extremely low amount of palladium nanoparticles on a core-shell framework by adopting a chemical impregnation method to obtain an electrode material; the loading capacity of noble metal palladium in the electrode material is only 0.29 percent, and the noble metal palladium is used as a cathode to be applied to the dechlorination reaction of the chloro-organic compound by electrocatalysis, and the mass activity is up to 44.39min^‑1g^‑1The conversion rate of dechlorination of the chlorinated organic compound can reach 94 percent at most, the electrocatalytic reaction activity is high, and the method has a wide application prospect in electrocatalytic hydrodechlorination.

Description

Inorganic-organic core-shell framework loaded low-dose noble metal palladium material, preparation thereof and application thereof in electrocatalytic dechlorination and hydrogenation reaction

Technical Field

The invention relates to an electrode material loaded with low-dose noble metal by an inorganic-organic core-shell framework, a preparation method and application thereof, in particular to a method for preparing the electrode material by TiO₂The @ PDA is a carrier loaded low-dose metal palladium electrode material, a preparation method thereof and application in electrocatalytic dechlorination and hydrogenation reactions.

Background

Chlorinated organic compounds (chlorophenol, polychlorinated pyridine acid, polychlorinated biphenyl and the like) are widely applied to the fields of chemical industry, medicine, pesticide and the like, have the characteristics of high toxicity, durability, biological enrichment and the like, are extremely difficult to convert in a biodegradation mode in the nature, and are easy to cause pollution to water, soil and underground water systems due to improper treatment. Therefore, how to effectively treat chlorinated organic pollutants is a problem which needs to be solved in long-term development of human beings.

In the prior art, the electrocatalytic reduction method has the advantages of good dechlorination effect, mild conditions and the like. Noble metal-based (including platinum, rhodium, palladium, etc.) materials are commonly used as catalysts in catalytic dechlorination, wherein palladium-based catalysts can intercalate hydrogen atoms into the crystal lattice of palladium to generate sufficient adsorbed hydrogen to facilitate the cleavage of C — Cl bonds, and thus are the most effective dechlorination catalysts. Therefore, noble metal palladium-based composites are often used as catalysts in electrocatalytic dechlorination reactions. For example, patent CN112657507A discloses a wrapped bimetallic catalyst with a core-shell structure, in which the core is active metal (palladium, platinum, iridium, nickel) nanoparticles, and the shell uses copper, tin, silver, zinc as a second metal carrier, such catalyst is used for hydrodechlorination reaction, and has high activity, stability and reaction selectivity. However, the active metal particles are generally 50-60 nm in size, so that the active metal particles are easy to agglomerate, the dispersibility is poor, the exposed catalytic area per unit mass of the active metal is small, and the mass activity of the active metal particles is not high. The invention patent CN108097249A also discloses a preparation method of a hydrodechlorination catalyst, which takes a mixed roasting product of diatomite and citric acid as a carrier, and the roasting product is dried and roasted again after being soaked in a palladium-containing salt solution, so that the catalyst can be used for hydrodechlorination of chloroacetic acid. The preparation process of the catalyst involves multiple times of roasting, the temperature is as high as 400-500 ℃, palladium metal particles are large, the unit load metal palladium amount is large, and the cost of the catalyst is high.

Because the resource of the noble metal is scarce and the noble metal is expensive, the cost of the noble metal catalyst with high dosage is high, and the noble metal catalyst cannot be applied to large-scale production. An effective solution to this dilemma is to prepare low-dose noble metal nanoparticles highly dispersed on a support having a nano-array structure. However, because noble metal nanoparticles are not thermodynamically stable, the noble metal nanoparticles are easy to agglomerate into large particles in the preparation process, effective reaction active sites are reduced, the reaction efficiency is reduced, the activity per unit mass is not high, and the highest mass activity of the existing catalyst is 8.5min^-1g^-1Therefore, the invention of a highly-dispersed low-dose noble metal catalyst is the key to the realization of dechlorination industrialization by an electrocatalytic reduction method.

Disclosure of Invention

The noble metal palladium nano-particles with high dispersity and low dosage are loaded, and a material with high specific surface area is required to be used as a carrier. The invention adopts the common TiO with the one-dimensional nanorod array structure grown on the FTO conductive glass₂It has large surface area, low synthesis cost, good chemical stability and other advantages.

As a load type electrocatalysis electrode material, strong binding force should exist between an active substance and a carrier, so that the stability of the electrode material in the electrolysis process can be ensured; meanwhile, the conductivity is also an important factor for investigating the performance of the electrode material. The invention selects polydopamine as a binder, and the dopamine is polymerized around the titanium dioxide one-dimensional nano-rod to form an inorganic-organic core-shell framework as a carrier for loading noble metal palladium nano-particles. On one hand, the polydopamine has a reducing effect and can reduce noble metal palladium into metal palladium particles from an ionic state without adding other reducing agents, and on the other hand, the polydopamine is a high-conductivity organic polymer and can be combined with TiO₂A strong binding force is formed.

Therefore, the invention provides a Pd nano-particle material with high dispersibility and low dosage loaded by an inorganic-organic core-shell framework and a preparation method thereof, and the Pd nano-particle material is used as an electrode for electrocatalytic dechlorination and hydrogenation reaction and shows higher electrocatalytic dechlorination capability and stability.

The technical scheme of the invention is as follows:

a preparation method of a low-dose noble metal palladium material loaded by taking an inorganic-organic core-shell framework as a carrier comprises the following steps:

(1) method for growing TiO on FTO conductive substrate by hydrothermal method₂Nanorod arrays

Immersing the FTO conductive substrate in hydrochloric acid aqueous solution of tetrabutyl titanate, carrying out hydrothermal reaction, and then calcining to obtain TiO with a nanorod array structure₂Material (denoted FTO/TiO)₂)；

In the hydrochloric acid aqueous solution of tetrabutyl titanate, the mass fraction of tetrabutyl titanate is 2-3 wt%, and the solvent is 15-37 wt% hydrochloric acid aqueous solution;

TiO with nano-rod array structure₂Vertically growing on the FTO conductive substrate as a carrier material;

(2) wrapping polydopamine on TiO by in-situ self-polymerization₂Around the nano-rod

Placing the material obtained in the step (1) in a dopamine solution, and soaking the material for 1-30 h (preferably 12h) at 10-80 ℃ (preferably 15 ℃) to allow dopamine to be polymerized on TiO with an array structure₂Around the nano-rod), then washing and drying to form poly-dopamine coated TiO₂Nanorod inorganic-organic core-shell framework material (denoted as FTO/TiO)₂@PDA)；

The concentration of the dopamine solution is 0.1-1.5 g/L, preferably 1 g/L; the solvent of the dopamine solution is Tris-HCl buffer solution, methanol or ethanol;

(3) uniformly dispersing and loading metal palladium nano particles on a polydopamine shell layer by adopting an in-situ reduction method

Putting the material obtained in the step (2) into a palladium salt solution, soaking for 5-20 h (preferably 12h) at 0-30 ℃ (preferably 15 ℃), then washing,drying to obtain the low-dose noble metal palladium material (written as FTO/TiO) taking the inorganic-organic core-shell framework as the carrier₂@PDA/Pd)；

The concentration of metal Pd in the palladium salt solution is 0.01-1 g/L, preferably 0.05 g/L; the solvent of the palladium salt solution is 0.1 to 0.2 weight percent of hydrochloric acid aqueous solution or 0.1 to 0.3 weight percent of NaCl aqueous solution; the palladium salt may be palladium chloride or the like.

The inorganic-organic core-shell framework prepared by the invention is used as a carrier to load a low-dose noble metal palladium material, and can be used as a cathode material to be applied to electro-catalytic hydrodechlorination of chlorinated organic compounds. The specific application method comprises the following steps:

an H-shaped electrode reaction tank is adopted as a reaction device, and an N117 cation membrane is adopted between a cathode reaction tank and an anode reaction tank to separate electrolyte (only cations are allowed to pass through a diaphragm, see the attached figure 1); the anode is made of graphite rod material, and the cathode is made of FTO/TiO₂@ PDA/Pd material; the electrolyte in the anode reaction tank is inorganic acid or inorganic alkali aqueous solution, and the electrolyte in the cathode reaction tank is chloro organic compound aqueous solution; carrying out electrocatalysis reaction by adopting a constant current electrolysis mode under stirring;

the electrocatalytic reaction conditions are as follows: constant temperature of 15-40 ℃ and constant current density of 1-10 mA cm^-2And the electrolysis time is 2-8 h.

Compared with the prior art, the invention has the advantages that:

TiO adopted in the invention₂The @ PDA inorganic-organic core-shell framework is used as a carrier, can provide a large surface area, controls the particle size of the metal palladium nanoparticles within the range of 1.2-2.0 nm, is highly dispersed on the carrier and is not agglomerated, and can provide more active sites participating in electrocatalytic reaction. Meanwhile, the size of the noble metal palladium nano-particles can be adjusted by controlling the thickness of the dopamine polymerization layer.

The preparation method greatly reduces the use amount of noble metal palladium, and has the advantages of simple process, environmental protection and atom economy. The catalyst shows higher unit mass activity in the electrocatalytic hydrodechlorination of chloro-organic compounds such as p-chlorophenol, 3, 6-dichloropicolinic acid and the like, and the mass activity can reach 44.39min at most^-1g^-1。

Drawings

FIG. 1 is a schematic view of an electrolytic cell apparatus according to an embodiment of the present invention.

FIG. 2 shows FTO/TiO prepared according to the first embodiment of the present invention₂SEM image of vertical nanorods.

FIG. 3 shows FTO/TiO prepared according to one embodiment of the present invention₂SEM image of @ PDA.

FIG. 4 shows FTO/TiO prepared according to one embodiment of the present invention₂TEM image of @ PDA/Pd.

FIG. 5 is a diagram showing the electro-catalytic dechlorination performance of p-chlorophenol in the first embodiment of the invention.

FIG. 6 is a liquid phase spectrum of p-chlorophenol after electrocatalytic dechlorination in the first embodiment of the present invention.

FIG. 7 is the liquid phase spectrum of 3, 6-dichloropicolinic acid after electrocatalytic dechlorination in example three of the present invention.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the details of the present invention will be further described with reference to specific examples, which are provided for illustration only and do not limit the scope of the present invention. The terminology used is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. The following describes the preparation method of the invention in detail with reference to the accompanying drawings and examples.

Example one

1. Preparation of TiO with nano-array structure₂Vertical nanorods. Soaking FTO conductive glass into hydrochloric acid aqueous solution of tetrabutyl titanate (the content of tetrabutyl titanate is 2.8%, and the solvent is hydrochloric acid aqueous solution with the concentration of 37 wt%), carrying out hydrothermal reaction for 5 hours at constant temperature of 150 ℃, washing, and calcining for 3 hours in air at constant temperature of 450 ℃ to prepare the FTO/TiO₂A material. FIG. 2 shows FTO/TiO₂SEM picture of (1), it can be seen that TiO₂Has a one-dimensional nanorod array structure, and is vertically grown on the FTO surface, and the average diameter of the nanorods is about 160 nm.

2.FTO/TiO₂Preparation of @ PDA. Mixing the above FTO/TiO₂Vertically arranged at a position containing 1.21g L^-1Tris-HCl and 0.5g L^-1Stirring in dopamine solution at constant temperature of 15 deg.C for 12 hr, and stirringWashing with deionized water, and drying to obtain FTO/TiO₂@ PDA. FIG. 3 is an SEM image of the prepared material, and it can be seen that dopamine has been present in each TiO₂Self-polymerizing the nano-rod surface into a thin layer to prepare the FTO/TiO₂@ PDA, the diameter of each nanorod is still kept at about 165nm, which indicates that the thin layer of PDA is within the range of 5-10 nm.

3.FTO/TiO₂Preparation of @ PDA/Pd. Mixing the above FTO/TiO₂@ PDA is vertically placed in a container containing 0.05g L^-1PdCl₂Stirring the solution for 12 hours at the constant temperature of 15 ℃, then washing the solution by deionized water, and drying the solution to obtain FTO/TiO₂@ PDA/Pd. FIG. 4 is a TEM image of the resulting material, which can be seen to be self-polymerized in TiO₂The average thickness of the PDA thin layer vertical to the surface of the nano rod is 5.23nm, the particle size of the Pd nano particles is about 1.5nm, and the Pd nano particles are uniformly dispersed in the PDA thin layer. The content of Pd nano-particles in the PDA thin layer is extremely low, and the loading amount of Pd is calculated to be 0.29%.

4. With FTO/TiO₂The material of @ PDA/Pd is used as a cathode for carrying out electrocatalytic dechlorination and hydrogenation on the p-chlorophenol. Adopting H-shaped electrode reaction tank, adopting N117 cation membrane to separate cathode and anode electrolyte, adopting graphite rod electrode as anode, and adopting the prepared FTO/TiO as cathode₂@ PDA/Pd material. The electrolyte in the anode reaction tank is a phosphoric acid buffer solution (pH is 3); the catholyte was 1mmol L^-1The pH of the p-chlorophenol solution was adjusted to 3.0 using phosphate buffer. The electrolyte is kept in a water bath at 30 ℃, and the electrolytic current is controlled at 6mA cm^-2And electrolyzed at constant stirring for 4 hours.

The detection is carried out by adopting high performance liquid chromatography, and the result of the detection shows that the conversion rate of the parachlorophenol is 94.04 percent, and the FTO/TiO₂The dechlorination mass activity of the @ PDA/Pd electrode can reach 44.39min^-1g^-1The electrode material is demonstrated to have excellent atom economy.

FIG. 5 shows the results of the performance of the electrolytic dechlorination of chlorophenol.

FIG. 6 shows the results of liquid chromatography detection of p-chlorophenol and phenol after electrolysis.

Example two

1.FTO/TiO₂Is perpendicular toAnd (4) preparing the nano rod. The preparation method and the process are the same as the first embodiment, and TiO with an array structure vertically grown on the surface of the FTO is obtained₂A one-dimensional nanorod.

2.FTO/TiO₂Preparation of @ PDA. The preparation method and process are the same as in example one, except that the dopamine concentration is 1.0g L^-1FTO/TiO thus obtained₂The thickness of the polydopamine thin layer of the one-dimensional nanorod is 12.15nm, which is higher than 5.23nm in the first embodiment.

3.FTO/TiO₂Preparation of @ PDA/Pd. The preparation method and the process are the same as the first embodiment except that the carrier adopts FTO/TiO with 12.15nm thickness of the polydopamine layer₂@ PDA, FTO/TiO therefrom₂The particle size of palladium nano-particles on @ PDA/Pd is about 2.0nm, and the loading amount of Pd is calculated to be 0.60%.

4. With FTO/TiO₂The @ PDA/Pd material is used as a cathode to carry out electrocatalytic dechlorination and hydrogenation on the parachlorophenol. The electrolysis process was the same as in example one except that the cathode used a polydopamine layer with a thickness of 12.15nm and a Pd loading of 0.60% FTO/TiO₂@ PDA/Pd material. Through measurement and calculation, the conversion rate of the parachlorophenol is 74.49 percent, and the dechlorination mass activity can reach 9.17min^-1g^-1。

EXAMPLE III

1. And (4) preparing a cathode material. The preparation method and the process are the same as those of the first embodiment, and the obtained result is the same as that of the first embodiment.

2. With FTO/TiO₂The material of @ PDA/Pd is used as a cathode to carry out electrocatalytic dechlorination and hydrogenation on the 3, 6-dichloropicolinic acid. Adopting H-shaped electrode reaction tank, adopting N117 cation membrane to separate cathode and anode electrolyte, adopting graphite rod material as anode, and adopting the prepared FTO/TiO as cathode₂@ PDA/Pd material. The electrolyte in the anode reaction tank is sodium hydroxide buffer solution (pH is 10); the catholyte was 1mmol L ^-13, 6-dichloropicolinic acid solution, the pH of which is adjusted to 10.0 with sodium hydroxide buffer. The electrolyte is kept in a water bath at a constant temperature of 30 ℃, and the electrolytic current is controlled at 5.0mA cm^-2And electrolyzed at constant stirring for 4 hours.

The conversion rate of the 3, 6-dichloropicolinic acid is 72.85 percent by detection and calculation by adopting high performance liquid chromatography.

FIG. 7 shows the results of liquid chromatography detection of dechlorination of 3, 6-dichloropicolinic acid after electrolysis.

Claims

1. A preparation method of a low-dose noble metal palladium material loaded by taking an inorganic-organic core-shell framework as a carrier is characterized by comprising the following steps:

(1) immersing the FTO conductive substrate in hydrochloric acid aqueous solution of tetrabutyl titanate, carrying out hydrothermal reaction, and then calcining to obtain TiO with a nanorod array structure₂A material;

(2) placing the material obtained in the step (1) in a dopamine solution, soaking for 1-30 h at 10-80 ℃, then washing, drying and in-situ self-polymerizing to form polydopamine-coated TiO₂Inorganic-organic core-shell framework material of nano-rod;

(3) and (3) placing the material obtained in the step (2) in a palladium salt solution, soaking for 5-20 h at 0-30 ℃, and then washing and drying to obtain the low-dose noble metal palladium material loaded with the inorganic-organic core-shell framework as a carrier.

2. The method for preparing a material with an inorganic-organic core-shell framework as a carrier and a low-dose noble metal palladium supported thereon according to claim 1, wherein in the step (2), the concentration of the dopamine solution is 0.1-1.5 g/L, and the solvent of the dopamine solution is Tris-HCl buffer, methanol or ethanol.

3. The method according to claim 1, wherein in the step (3), the concentration of Pd in the Pd salt solution is 0.01-1 g/L, and the solvent of the Pd salt solution is 0.1-0.2 wt% of hydrochloric acid solution or 0.1-0.3 wt% of NaCl solution.

4. The method for preparing a material with an inorganic-organic core-shell framework as a carrier and a low-dosage noble metal palladium supported thereon according to claim 1, wherein in the step (3), the palladium salt is palladium chloride.

5. The method for preparing the Pd/Pd alloy material by the method of claim 1, wherein the Pd/Pd alloy material is loaded on the inorganic-organic core-shell skeleton.

6. The use of the inorganic-organic core-shell structure as a carrier to load a low-dose noble metal palladium material as a cathode material in an electrocatalytic hydrodechlorination reaction of chlorinated organic compounds as claimed in claim 5.

7. The application of claim 6, wherein the method of applying is:

an H-shaped electrode reaction tank is adopted as a reaction device, and an N117 cationic membrane is adopted between a cathode reaction tank and an anode reaction tank to separate electrolyte; the anode is made of a graphite rod material, and the cathode is made of a low-dose noble metal palladium material loaded by taking the inorganic-organic core-shell framework as a carrier; the electrolyte in the anode reaction tank is inorganic acid or inorganic alkali aqueous solution, and the electrolyte in the cathode reaction tank is chloro organic compound aqueous solution; carrying out electrocatalysis reaction by adopting a constant current electrolysis mode under stirring;